Two distinct morphological types of malignant lymphoma in the same patient occur mostly due to transformation of a low grade lymphoma (CLL) into a large - cell non-Hodgkin lymphoma (highgrade lymphoma). Later reports have brough evidence of a clonal relationship between CLL and supervening NHL. The Richter´s syndrome was found to be more frequent in patients with CLL displaying either multiple chromosomal aberrations or monoclonal gammapaties. In the last two decades reports have evidenced the existence of two types of the Richter´s syndrome: one, the “classical” as a terminal event in a long evolving CLL, the other “variant” as the first clinical manifestation of a previously unrecognized subclinical CLL. Aggressive chemotherapy of CLL play a role in transformation of CLL to Richter´s syndrome.

        Key words: Richter´s syndrome - Malignant lymphoma - Transformation - CLL